Chapter 15: Relating Small Angle Scattering and Analytical Ultracentrifugation in Multidomain Proteins

1.1 Scope of This Chapter

This chapter compares the major features of X-ray and neutron solution scattering ^{[1] [4]} with analytical ultracentrifugation in application to multidomain proteins. ^{[5] , [6]} It illustrates the utility of joint scattering and ultracentrifugation studies by presenting recent examples from our own work. This chapter expands previous brief reviews on multidomain proteins in the complement system of immune defence. ^{[4] , [5]} The proteins of interest can be categorised into four types. Type 1 proteins possess no covalent linker between domains within the protein. Type 2, Type 3 and Type N proteins comprise two-, three- or multidomain proteins in that order, with one, two or more linkers, respectively, connecting these domains. The word domain usually refers to a single, independently folded protein subunit. In this chapter, this term is also used to describe an essentially rigid multidomain fragment (such as the four domains within the Fab or Fc fragments of an antibody, but not the intact antibody itself) or an oligomer containing as many as four or five protomers.

From a biological standpoint, large multidomain proteins with many linkers between many domains represent an important and common set of proteins. The existence of long linkers between the domains is thought to preclude the crystallisation of many multidomain proteins. If crystals are obtained, the resulting multidomain structure may possess large conformational artefacts which need to...